This invention relates to a tool retention mechanism for retaining a tool holder and its associated tool in a drive spindle against axial movement.
There are a number of tool retention mechanisms available in the prior art for rigidly holding the knob of a tool holder against axial movement within a drive spindle. For safety purposes, these tool retention mechanisms employ a long array of belleville washers to provide a large holding force for gripping the tool holder knob. This invention was developed out of the need to package the tool retention mechanism in a compact housing which is both shorter and narrower than prior art structures. Because compactness is one of the design requirements, this invention utilizes a unique arrangement and cooperation between two coaxially mounted sets of belleville washers.
A tool retention mechanism constructed in accordance with the principles of this invention is assembled in a housing having an elongate internal compartment with an opening at one end. A elongate rod member is supported lengthwise in the compartment and supports at one end a knob clamping assembly which is formed by a circular array of claw fingers that are spring biased to close together. A first piston is slideably disposed on the rod behind the claw fingers and has a cylindrical collar portion which is adapted to engage the claw fingers as it is moved outwardly to and hold them in a knob clamping position. A second piston is secured to the inner end of the rod member. A first spring biased means is provided for exerting a constant force along the rod member in a direction inwardly of the compartment and a second spring biased means exerts a constant force on the cylindrical collar portion in an outward direction of the compartment. A fluid control means is provided for selectively and sequentially driving the second piston means to overcome the force exerted by the first spring bias means and driving the first piston means from the extend position to the retract position.